For many years concrete walls or foundations have been produced by casting concrete between two form walls made of wood, aluminum, steel, or other materials. Form walls require a connection called a form tie to hold the form walls together. Traditionally, form ties have been made using metals that are corrosive and very conductive. Generally, the form ties are either left in place after the forms are removed and then broken off at the concrete surface or removed from the wall. In the circumstance where the ties are removed, the form ties must first be treated with a bond breaker, such as grease. When the form ties are removed from the wall, the bond breaker must also be removed and the remaining hole must be plugged with an expansive grout or some other material. One type of concrete wall, a concrete sandwich wall, includes a layer of insulation and two layers of concrete, termed concrete wythes, one on each side of the insulation. In the event the walls are insulated, it is also necessary to replace the insulation prior to plugging and waterproofing the holes left by removing form ties of the prior art.
Moreover, in the case of breaking the form ties off at the surface and leaving them in place, corrosion of the remaining form tie may occur when exposed to moisture. Once corrosion begins, swelling of the corrosion may damage the wall, especially during freeze/thaw cycling. This may ultimately cause a leak that will allow moisture to penetrate the wall. Additionally, corrosion of metal form ties may lead to staining of interior and exterior wall surfaces. Further, the metallic ties create conductive paths through which large amounts of energy may be lost within a heated structure. In the event that the wall is insulated, the conductive paths may significantly reduce the efficiency of the insulation system. Furthermore, ties that are broken off at the surface have traditionally had a relatively low tensile strength.
Accordingly, there is a need in the art for a form tie that is neither corrosive nor highly conductive, and may also remain in the finished product without causing corrosion or compromising the thermal integrity of the structure. Further, there is a need in the art for a form tie that eliminates the extra steps of removing the form tie and plugging the hole that is left behind, leading to increased efficiency in the building process. There is also a need in the art for a form tie that can be broken off at the surface of the building component, yet has a high tensile strength.
As discussed above, the form ties of the prior art are often made of metal, which is undesirable in the finished building product. The prior art also includes form ties made of a composite material, which are sometimes left in the resulting building component. The prior art composite form ties require elaborate clamp devices to hold the form ties in place and allow the assembly to carry the load of the wet concrete. Sometimes, these elaborate ties include screw threads and wedge assemblies that either weaken the ability of the form tie to carry the load of the concrete and/or allow concrete to penetrate the parts of the clamp device, which ruins the clamp device after only a few uses. Furthermore, the form ties and clamp devices of the prior art are not able to take advantage of the full strength capacity of prior art form ties, which leads to the need to use many form ties of the prior art in a structure. Factors contributing to the ability to take advantage of the strength capacity of the form tie include, but are not limited to, the surface area of the form tie that the clamp device grips, how the clamp device grips the form tie, and the length of the form tie. In some cases, the form ties of the prior art get their strength capacity from the attached clamp device. The lower strength capacity of these form ties of the prior art can lead to slippage and/or failure of the tie. Accordingly, there is a need in the art for a form tie and clamp device that take advantage of as much of the strength capacity of the form tie as possible, do not weaken the ability of the form tie to carry the necessary loads, can be used to construct taller walls than form ties of the prior art, can be used in fewer numbers than form ties of the prior art in a given structure, and that do not allow concrete to penetrate parts of the clamp device, resulting in a clamp device that may be reused much more than the clamp devices of the prior art.